With the development of the Internet, communication devices, such as switches, modems and routers, have been wildly developing. Due to a large amount of signal transmission, a communication device usually configured with a plurality of board-type RF components on a circuit board to receive signals having respective different frequencies on one frequency band and then to add the signals together so as to increase the signal transmitting amount on one frequency band. However, the board-type RF component on the circuit board is an electronic component with small size such that it is with comparatively poor signal quality. Therefore, an extra transmission component such as a coaxial cable or an antenna is required to externally connect to the board-type RF component for strengthening the transmitting signal. A coaxial connector is therefore provided to connect the board-type RF component with the transmission component in such a manner that the coaxial connector is connected between the board-type RF component and a casing of the communication device to which a transmission component is connected.
However, with the development of communication devices, communication devices have been evolved from using a single frequency band to multiple frequency bands for data transmission in recent years, such that a dual-frequency band communication device that can transmit and receive signals in two frequency bands is available today. In practice, such dual-frequency band communication device requires two board-type RF components on the circuit board for two frequency bands, and accordingly at least two coaxial connectors on the casing are required. However, the space of the casing for receiving the coaxial connectors is limited such that the casing is not able to accommodate as many as more than two coaxial connectors.